Loudspeaker baffle assembly



May 14, 1963 v P. J. MORGILLO 3,089,562

LOUDSPEAKER BAFFLE ASSEMBLY Filed Oct. 1, 1959 2 Sheets-Sheet 1 INVENTOR. PELLEGFQINO JOSEPH MOEGILLO BY www HTTOFENEY May 14, 1963 P. J. MORGILLO 3,089,562

LOUDSPEAKER BAFFLE ASSEMBLY Filed Oct. 1, 1959 2 Sheets-Sheet 2 INVENTOR. PELLEGEINO JOSEPH MORGILLO ,QTTOENEY United States Patent 3,089,562 LOUDSPEAKER BAFFLE ASSEMBLY Pellegrlno Joseph Morgillo, Plainview, N.Y., assignor to Lafayette Radio Electronics Corporation, a corporation of New York Filed Oct. 1, 1959, Ser. No. 843,780 8 Claims. (Cl. 181-31) My invention relates to a loudspeaker baflie assembly.

In electrically operated loudspeakers, electric impulses generated by a sound track or other source are transformed by an electromagnetic transducer within a cabinet into mechanical vibrations. These vibrations are imparted to the apex of a hollow cone, flexibly supported forwardly at its base in a baflle plate at the forward end of the cabinet in such manner that it vibrates longitudinally of its axis of generation. Each forward movement generates a compression wave in the airin front of the cone and each rearward movement generates a wave of reduced pressure in this air, the alternate compression and reduced pressure waves constituting the sound wave. The sound waves pass from the cabinet through an elliptical opening in the front wall of the cabinet.

. Similarly, alternate compression and reduced pressure waves are generated from the rear face of the cone but of opposite phase from those in front of the cone, the forward movement of the cone generating a reduced pressure wave and the rearward movement a compression wave. The sound waves from the rear of the cone are brought into phase with those from the front of the cone by leading them from the space within the cabinet back of the cone to a space between the front wall of the cabinet and the baffle plate, the length of the path of these rear sound waves being equal to one half the wave length of the sound waves at approximately the middle of the range of tones of the cone. These waves from the rear of the cone are in phase with those from the front of the cone and if directed in the same direction would reinforce the sound waves from the front of the cone thereby giving the loud speaker greater power.

The sound waves passing over the front surface of the baflle plate have a tendency to cling to the surface of the plate even to the opening and to turn inwardly at the opening and, opposing the sound waves coming from the front of the cone, reduce the power of the loud speaker.

My invention provides means, whereby these sound waves are directed forwardly, in the direction of the sound waves from the front of the cone to reinforce the latter and increase the power of the loudspeaker.

In any invention I provide about the circular opening in the baflie plate and extending forwardly thereof an annular deflecting flange the outer surface of which slopes radially inwardly and forwardly. The slope of this surface is most effective at an angle of 45 to the plane of the bafile plate but for particular conditions may vary from 45 The opening in the front wall is of a generally elliptical shape with the minor axis equal to the diameter of the opening in the baflle plate, the centers of both openings being on a common axis. This provides a pair of diametrically opposite crescent shaped openings for the sound waves from the back of the cone. The sound waves from the front and from the back of the cone thus proceed forwardly approximately in phase and without interference.

The various features of the invention are illustrated, by way of example, in the accompanying drawings, in which:

FIG. 1 is a vertical section of the forward part of a loud speaker cabinet and of the baffle assembly of my invention taken through the common axis of the cone and the b'affle plate and front wall openings;

, Patented May 14, 1963 FIG. 2 is a front elevation of the cabinet showing the front wall and the baffle plate, parts being broken away to show interior details, and

FIG. 3 is a vertical section of the apparatus similar to that of FIG. 1.

In the embodiment of the invention shown in the accompanying drawings, the loudspeaker .baffle assembly is illustrated as mounted in a cabinet 10 having a front wall 11. This front wall may have a molding 12 about its front edge for the purpose of appearance or reinforcement. A b affle plate 13 is mounted to the rear of the front wall 11 and spaced therefrom to form a space 14. The outer edges of the bafile plate are also spaced from the side Wall of the cabinet to form a passage 15 from the rear of the baffle plate to the passage 14.

The baflle plate 13 may serve as a mounting and suppont for a cone and an electromagnetic transducer. For this purpose a basket 16 may be mounted on the rear face of the baffle plate 13 extending rearwardly to mount the transducer 17 and the vibrating cone 18.

The rear end or apex of the cone is supported by a spider 19 which may comprise springs at circumferentially spaced intervals to enable the cone to vibrate forwardly and backwardly under the action of the transducer. The front end or base of the cone is supported for vibratory forward and rear movements by a surround 20 of flexible sheet material the outer margin of which is engaged between the front edge of the basket and the rear face of the baflle plate 13 a gasket 21 of a dead material being interposed between the marginal edge of the surround and the back face of the baffle plate to deaden any vibrations that might be transmitted through the surround from the cone.

The vibrations from the front or interior surface of the cone pass through an opening 22 in front of and co-axial with the cone and thence through an opening 23 in the front Wall of the cabinet. Vibrations from the rear surface of the cone are transmitted through openings 24 in the basket, thence from the rear part of the cabinet through the passages 15 and 14 toward the opening 22 in the baffle plate. These vibrations are deflected by means of an annular flange 25 enclosing the periphery of the opening 22 and extending forwardly toward or to the front wall 11. The annular flange 25 has a sloping outer annular surface 26, the angle of slope being preferably 45 to the surface or plane of the baflle plate.

The opening 22 is circular and centered on the axis of the cone 18, and the annular wall 25 is also circular. As shown in FIG. .2 the opening 23 of the front Wall is of a generally elliptical shape having its minor axis about equal to the diameter of the opening 22. There is thus formed a pair of crescent shaped passages 27 and 28 diametrically positioned on opposite side of the periphery of the opening 22.

The sound waves from the rear of the cone which were originally in opposite phase to the sound waves of the front surface of the cone are brought into phase with the vibrations of the front of the cone by making the length of the path from the rear of the cone through the passages 15 and 14 equal to one-half wave length of the tones in the intermediate range of the cone 18. This is a well known expedient in the art. Consequently when a compression wave starts from the front surface of the cone a compression wave from an adjacent cycle arrives from the rear of the cone and being deflected forwardly through the passages 27 and 28 moves forwardly together with the compression wave from the front surface of the cone. The crescent shape of the openings 27 and 28 facilitates this forward movement brought about by the deflector 25 so that sound waves from the rear of the cone and those from the front of cone flow parallel and without impinging one on the other. The power of the loudspeaker is thus brought to its maximum efliciency.

It will be apparent that the intermediate tone Whose wave length has been used to determine the length of path from the cone to the opening 23 will be among the low tones of the cone, namely those in the range in which the cone would act as a woofer for a high fidelity loudspeaker. The tones coming from the tweeter and whizzer are not influenced by the passage between the baffle plate and the front wall.

Having described my invention, what I claim is:

1. A baflle plate assembly for loudspeakers which comprises, a front wall having an opening, a baflle plate spaced rearwardly of said wall and having an opening of lesser area than that of the opening in the front wall and centered on a common axis therewith and a deflecting flange on said baffle plate about the periphery of the opening therein and extending forwardly toward said front wall.

i2. The baflle plate assembly of claim 1 in which the opening in the baifle plate is circular and in which the vopening in the front wall is of a generally elliptical shape having a minor axis approximately the same as the diameter of the opening in the bafl le plate.

3. The baffle plate assembly of claim 2 in which the outer surface of the deflecting flange is at an angle of approximately 45 to the plane of the baflle plate.

4. A loudspeaker comprising a cabinet having a front wall, said front wall having an opening, a baflie plate spaced rearwardly of said front within said cabinet and having an opening of lesser area than that of the opening in the front wall and centered on a common axis therewith, said cabinet having a passage from the interior of the cabinet back of said baffle plate with a space between said bafl'le plate and said front wall, and a deflecting flange on said baflle plate about the periphery of the opening therein and extending forwardly toward said front wall said cabinet being closed except for the said passage and said opening in said front wall.

5. The loudspeaker of claim 4 in which said opening in said baflle plate is circular and the opening in said front wall is of a generally elliptical shape having its minor axis approximately equal to the diameter of said circular opening.

6. The loudspeaker of claim 5 in which the outer'surface of said deflecting flange is at an angle of 45 to the plane of the baffle plate.

7. The loud speaker of claim 6 having a supporting basket mounted on the rear wall of said baflle plate and a transducer and vibrating cone mounted on and within said basket.

8. The loudspeaker of claim 7 in which the length of the passage from the interior of the cabinet back of the baflle plate to the opening in the baflle plate is equal to one half of the wave length of tones in the intermediate range of said cone.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A BAFFLE PLATE ASSEMBLY FOR LOUDSPEAKERS WHICH COMPRISES, A FRONT WALL HAVING AN OPENING, A BAFFLE PLATE SPACED REARWARDLY OF SAID WALL AND HAVING AN OPENING OF LESSER AREA THAN THAT OF THE OPENING IN THE FRONT WALL AND CENTERED ON A COMMON AXIS THEREWITH AND A DEFLECT- 